Two-stroke internal combustion engines such as those used in chainsaws, brushcutters, and the like, are often equipped with carburetors for mixing and supplying air and fuel to the engine. Some scavenging carburetor arrangements may have separate air-fuel passages and air passages that may help reduce, and often prevent, undesirable flow-through and fuel-loss through its exhaust. Some of these arrangements may not generate air and fuel mixtures that are lean for an idle operating condition, for startup, or for other low speed and low load operating conditions. And some of these arrangements may generate air and fuel mixtures that are too lean upon a rapid acceleration of the internal combustion engine.